Brushless DC Motor Control With Integrated Water in Filter Circuitry

ABSTRACT

A filter assembly combines the physical support, protection and electrical connections for a water in filter (WIF) circuit with the support, enclosure and electrical connections used for a motor control circuit that drives a BLDC motor in the filter assembly. Sharing space and electrical connections between what have been physically separate electronic circuits reduces the cost, materials and parts necessary to manufacture the filter assembly. In an assembly with a brushless motor-driven pump, the electrical connections from the host equipment to the motor can be shared with the WIF circuit, eliminating separate conductors and connectors.

BACKGROUND

The disclosure relates to fuel filter systems, and particularly to fuelfilter systems incorporating a brushless motor-driven pump andcomponents for detecting accumulated water in the filter housing.

Fuel filtration systems are constructed to remove particulates and waterfrom fuel delivered to systems such as internal combustion engines.Separated water accumulates in fuel filter assembly housings and must beperiodically removed. A common method of detecting the amount of wateris to employ electrodes positioned to sense the electrical resistance offluid within the filter housing. The electrical resistance of water isfar less than the electrical resistance of hydrocarbon fuels such asdiesel fuel, so water contacting the electrodes produces a detectablechange in current flow between the electrodes. This change in electricalresistance is used to generate a signal communicated to servicepersonnel, automatic water drain systems, and/or the vehicle operatorthat accumulated water has reached a level that must be drained. Thefilter assembly incorporates a water in filter (WIF) circuit thatreceives power, electrically connects the sensor in a path where thechanges in electrical resistance at the sensor can be detected at theWIF circuit, and provides an electrical signal compatible with vehiclesystems that provide indicators for service or operators, or for use byautomatic water drain apparatus.

Fuel filter assemblies frequently incorporate a motor driven pump tomove fuel through the filter enclosure and filter media, providing apre-determined flow of clean fuel at a defined pressure to downstreamsystems such as high pressure fuel injection pumps and fuel injectionsystems. The motor driving the pump may be of the brushed or brushlesstype, with either form of motor requiring at least one electricalconnector to power the motor. Brushless direct current (BLDC) motorsrequire a motor control circuit that is typically arranged within themotor/pump housing or on the filter assembly close to the BLDC motor. Itis common for prior art filter assemblies to have two electricalconnections to the equipment to which the filter assembly is connected,a first electrical connector for the WIF circuit and a separateelectrical connector to the motor that drives the pump.

There is a need in the art for a filter assembly that reduces the partcount and simplifies the electrical interface between the filterassembly and host equipment.

SUMMARY OF THE INVENTION

A filter assembly according to aspects of the disclosure combines thephysical support, protection and electrical connections for a WIFcircuit with the support, protection and electrical connections used fora motor control circuit that drives a BLDC motor in the filter assembly.Sharing space, electrical connections between what have been physicallyseparate electronic circuits reduces the cost, materials and partsnecessary to manufacture the filter assembly. In an assembly with abrushless motor-driven pump, the electrical connections from the hostequipment to the motor can be shared with the WIF circuit, eliminatingseparate conductors and connectors.

In one embodiment, the WIF circuit shares electrical connections for alift pump in a fuel filter assembly, resulting in a single electricalconnector to the host equipment.

In one embodiment, the WIF circuit is mounted to the same printedcircuit board as a motor control circuit for a pump included in thefilter assembly.

In one embodiment, the filter assembly includes a pocket sealed fromfluid flowing through the filter assembly, a motor control circuit isconstructed on a printed circuit board mounted in said pocket and a WIFcircuit is constructed on the same printed circuit board as the motorcontrol circuit.

In one embodiment, the WIF and motor control circuit are constructed onthe same printed circuit board, but operate independently of each other.

In one embodiment, the WIF and motor control circuit are constructed onthe same printed circuit board, and the WIF transmits a water presentsignal to the motor control circuit.

Alternative embodiments of the disclosed filter assembly may incorporateone or more of the disclosed features and relationships included in thedetailed description below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view through a filter assembly illustratingseparate circuit boards, electrical connections and locations for WIFand motor control circuits; and

FIG. 2 is an exterior view of a filter assembly where the WIF circuitand motor control circuit share the same space and electricalconnections according to aspects of the disclosure.

DETAILED DESCRIPTION

FIG. 1 illustrates a filter assembly 10 incorporating a water-in-filter(WIF) circuit 12 and related water sensor 14. The water sensor 14 issituated in a water bowl 16 suspended from the lower end of a filtercartridge 18.

A connector 13 and wires bring power and ground to the WIF circuit 12and send a “water present” signal from the WIF circuit 12 to othersystems, where the water present signal may be used to light anindicator or activate an automated water drain mechanism. The filterassembly includes a filter head 20 that receives the filter cartridgeand defines fluid flow paths into and away from the filter cartridge 18.The upper end of the filter head 20 mounts a brushless direct current(BLDC) motor 22 and pump 23 enclosed in a housing 24 mounted to the topof the filter head 20. The housing 24 cooperates with a cover 25 todefine a sealed pocket 27 for a control board 28. The control board 28includes a control circuit 30 that generates the rotating magnetic fieldto drive the BLDC motor 22 at a rotational speed sufficient to providefuel flow to meet demand from downstream systems. A connector 32delivers power and ground to the control board 28 for use by the controlcircuit 30.

The BLDC motor 22 drives the pump 23 to circulate fuel from a supplyreservoir through the filter cartridge 18 and out of the filter assembly10 to downstream systems such as high pressure fuel pumps or fuelinjection systems. As fuel passes through the filter cartridge 18, wateris separated from the fuel and falls to the bottom of the filtercartridge 18, where it passes through a drain opening 26 into the waterbowl 16. The water sensor is arranged to detect a level of wateraccumulation in the water bowl 16, and the WIF circuit is constructed tomonitor the condition of the water sensor 14 and generate the “waterpresent” signal indicating a need to drain water from the water bowl 16.

The filter assembly shown in FIG. 1 requires two separate PC boards, twoenclosures for the boards, two sets of conductors and connectors for theseparate WIF circuit 12 and motor control board 28.

FIG. 2 illustrates an alternative filter assembly 100, which is similarin structure and function to the filter assembly 10 described above. Afilter head 120 mounts a filter cartridge 118 and defines fluid flowpaths from a fuel reservoir to the filter assembly 100, through thefilter cartridge, and away from the filter assembly 100 to downstreamsystems. A water bowl 116 is suspended from the bottom of the filtercartridge 118 and in fluid communication with the interior of thecartridge 118. Water separated from the fuel flowing through thecartridge descends into the water bowl through a drain in the bottom ofthe cartridge housing, as shown in FIG. 1. A water sensor 114 isarranged in the water bowl 116 to detect a pre-determined quantity ofaccumulated water. The filter assembly 100 also employs a BLDC motordriven pump surrounded by a housing mounted to the top of the filterhead 120 as shown in FIG. 1. The motor/pump housing cooperates with acover 125 to secure a PC board 128 in a sealed enclosure, as shown inFIG. 1.

In the embodiment of FIG. 2, the WIF circuit 112 is arranged on the samePC board 128 as the motor control circuit 130. The circuits 112, 130 canshare the power and ground from connector 132, but may otherwise befunctionally separate circuits. It may be necessary to provide somebuffering, shielding, and/or noise protection for the WIF circuit 112,given its close proximity to the active motor control circuit 130.Connector 132 may be a four conductor arrangement with room for power,ground, incoming signal from the water sensor 114 and an outgoing “waterpresent” signal. This disclosed arrangement significantly reduces thepart count and cost of connecting the filter assembly 100 to the hostequipment (not shown).

It is possible to employ fluid pressure generated by the BLDC motordriven pump to evacuate water from the water bowl. In such anarrangement, the water present signal from the WIF circuit 112 could beeasily transmitted to the motor control circuit 130 to initiate a waterevacuation cycle. In the embodiments of FIGS. 1 and 2, the water presentsignal is transmitted to the host equipment. In an alternativeembodiment that employs the filter assembly pump to evacuate water, thefilter assembly may be effectively “self-contained”, where waterdetection and water evacuation are handled by the filter assemblyitself. This would eliminate the need to transmit the water presentsignal to the host equipment and potentially simplify the interfacebetween the filter assembly and the host equipment still further.

What is claimed:
 1. A fuel filter assembly comprising: an electric motorconnected to drive a pump to circulate fuel through filter mediacontained in a filter enclosure; a water accumulation chamber in fluidcommunication with said filter enclosure and situated where waterseparated from said fuel passing through said filter media descends intosaid water accumulation chamber; a sensor in said water accumulationchamber and configured to detect the presence of a pre-determinedquantity of water in said water accumulation chamber; a water in fuelcircuit connected to monitor said sensor and generate a water presentsignal when said pre-determined quantity of water is detected; whereinsaid electric motor and said water in filter circuit are connected to ahost equipment by the same electrical connector.
 2. The fuel filterassembly of claim 1, wherein said electric motor is a BLDC motor andsaid filter assembly includes a motor control circuit to drive said BLDCmotor, said motor control circuit and said water in filter circuit beingmounted to a common PC board.
 3. The fuel filter assembly of claim 2,wherein said PC board is located in a compartment defined by a housingthat surrounds the electric motor and pump.
 4. The fuel filter assemblyof claim 2, wherein said motor control circuit and water in filtercircuit share power and ground but are otherwise functionally separate.